You're better off self managing or going with a local company with boots on the ground.

Account holders can't take any write-offs personally for investments made in the 401k.

My first property was paid off making me only $1000/month profit.

We've thought about trying to sell off each unit.

I look every day for off market houses to flip.

I strongly recommend getting involved with your local REI meetup groups so you can work out your pitch with help from other landlords.I hope this doesn't come off the wrong way without tone or facial expressions behind it. 

Look for motivated sellers off market and market via cold calling and or direct mail, geofencing, advertising and the like.A good wholesaler is as @Ericka Parrott mentioned, direct to seller, did good underwriting and can deliver an actual "Deal" whether buy and hold or flip. 

First off congrats for looking into this realy estate stuff at such an early age! 

How do you write things off?

Essentially, instead of being able to write it off immediately, it lowers the purchase price for tax purposes, meaning depreciation will be calculated on a slightly lower amount over time.